Method for listening on uplink channel and apparatus

ABSTRACT

Example communication methods and apparatus are described. One example method includes performing first listen before talk (LBT) and sending a first data packet on a first uplink burst after the first LBT succeeds. A second contention window size is determined based on the first contention window size and a first reference time unit. Second LBT is performed based on the second contention window size. The first contention window size is used for a LBT previous to the second LBT, the first reference time unit is later than the second reference time unit corresponding to the first uplink burst. The first reference time unit is a time unit for determining the second contention window size, or a starting time unit of a second uplink burst corresponding to the second LBT. The second reference time unit corresponding to the first uplink burst is a time unit in the first uplink burst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/828,332, filed on Mar. 24, 2020, which is a continuation ofInternational Application No. PCT/CN2017/103176, filed on Sep. 25, 2017.All of the afore-mentioned patent applications are hereby incorporatedby reference in their entireties.

TECHNICAL FIELD

This application relates to the communications field, and in particular,to a method for listening on an uplink channel and an apparatus in thecommunications field.

BACKGROUND

A licensed-assisted access using long term evolution (licensed-assistedaccess using Long Term Evolution, LAA-LTE) technology (that is, an LAAtechnology) is introduced into Release 13 in the fourth generation (4G)mobile communications technology, and an enhanced licensed-assistedaccess (enhanced licensed-assisted access, eLAA) technology isintroduced into Release 14. In the LAA technology and the eLAAtechnology, an available spectrum may be extended to a 5 GHz unlicensedband by using a carrier aggregation (carrier aggregation, CA)technology. With assistance of a licensed spectrum, a network device anda terminal device may transmit downlink information and uplinkinformation on an unlicensed spectrum. Based on the LAA and eLAA, theMultefire 1.0 standard further implements uplink and downlinktransmission in an LTE system completely on an unlicensed spectrumwithout relying on assistance of a licensed spectrum. In a future fifthgeneration new radio (fifth generation New Radio, 5G NR) system,transmission on an unlicensed spectrum also exists.

To implement fair coexistence with network devices and terminal devicesof different operators and inter-RAT such as Wi-Fi radio nodes on anunlicensed spectrum, the LAA, the eLAA, and a Multefire system use alisten-before-talk (listen before talk, LBT) channel access mechanism,in which listening on a channel is required before a network deviceperforms downlink transmission or a terminal device performs uplinktransmission. A listening manner includes clear channel assessment(clear channel assessment, CCA) of random backoff, and a value of aninitial random backoff counter of the CCA is determined by a contentionwindow size (contention window size, CWS). For scheduling-based uplinktransmission, the terminal device dynamically adjusts the CWS based onhybrid automatic repeat request (hybrid automatic repeat request, HARQ)status information fed back by the network device, to adapt to a channelstatus and fairly coexist with a contention node.

In a further enhanced licensed-assisted access (Further enhancedlicensed-assisted access, FeLAA) system and a Multefire 1.1 system thatare introduced into Release 15, a grant-free uplink (Grant-free Uplinkor Grantless Uplink, GUL) transmission mechanism, or referred to as anautonomous uplink (Autonomous UL, AUL) transmission mechanism, isintroduced. The terminal device does not need to send a schedulingrequest (scheduling request, SR) and wait for an uplink grant (ULgrant). Instead, the terminal device may directly send uplink data on anAUL resource after LBT succeeds, thereby eliminating channel listeningfor the SR and the UL grant. For the grant-free uplink transmission,after the terminal device sends the AUL transmission, the network devicemay not correctly receive the AUL transmission of the terminal deviceand does not identify the corresponding terminal device. Consequently,the terminal device cannot receive any HARQ status information. Anuplink CWS adjustment criterion in the prior art is not applicable tothe scenario in which the terminal device cannot receive the HARQ statusinformation in AUL transmission, and cannot resolve a channel adaptationproblem of the terminal device in AUL transmission.

SUMMARY

Embodiments of the present invention provide a method for listening onan uplink channel and an apparatus, to provide an uplink CWS adjustmentmethod.

According to a first aspect, an embodiment of the present inventionprovides a method for listening on an uplink channel. In the method, theterminal device performs first listen before talk LBT, and sends a firstdata packet on a first uplink burst after the first LBT succeeds. Theterminal device determines a second contention window size CWS, andperforms second LBT based on the second CWS.

In a first manner, on condition that a first time length is greater thanor equal to a first time threshold, and the terminal device does notreceive first indication information indicating an HARQ status after thefirst uplink burst, the second CWS is greater than a first CWS. Forexample, the second CWS may be 7, and the first CWS may be 3.

In a second manner, on condition that a first time length is less thanor equal to the first time threshold, and the terminal device does notreceive the first indication information indicating the HARQ statusafter the first uplink burst, the second CWS is equal to the first CWS.

In a third manner, on condition that the first time length is less thanor equal to the first time threshold, and the terminal device does notreceive the first indication information indicating the HARQ statusafter the first uplink burst, the second CWS is determined based onsecond indication information, where the second indication informationis indication information that is received by the terminal device beforethe first uplink burst and that is used to indicate the HARQ status.

An interval between a first reference time unit and a second referencetime unit that corresponds to the first uplink burst is a first timelength, the first CWS is a CWS corresponding to LBT previous to thesecond LBT, and the first reference time unit is later than the secondreference time unit.

According to a second aspect, an embodiment of the present inventionprovides a wireless apparatus. The apparatus includes a processor, and amemory and a transceiver that are coupled to the processor.

The processor is configured to perform first listen before talk LBT; thetransceiver is configured to send a first data packet on a first uplinkburst after the first LBT succeeds; and the processor is furtherconfigured to determine a second contention window size CWS.

In a first manner, on condition that a first time length is greater thanor equal to a first time threshold, and the wireless apparatus does notreceive first indication information indicating an HARQ status after thefirst uplink burst, the second CWS is greater than a first CWS.

In a second manner, on condition that a first time length is less thanor equal to the first time threshold, and the wireless apparatus doesnot receive the first indication information indicating the HARQ statusafter the first uplink burst, the second CWS is equal to the first CWS.

In a third manner, on condition that the first time length is less thanor equal to the first time threshold, and the wireless apparatus doesnot receive the first indication information indicating the HARQ statusafter the first uplink burst, the second CWS is determined based onsecond indication information, where the second indication informationis indication information that is received before the first uplink burstand that is used to indicate the HARQ status.

The processor is further configured to perform second LBT based on thesecond CWS.

An interval between a first reference time unit and a second referencetime unit that corresponds to the first uplink burst is a first timelength, the first CWS is a CWS corresponding to LBT previous to thesecond LBT, and the first reference time unit is later than the secondreference time unit.

It should be noted that the foregoing three manners may be used asindependent solutions, or any two of the foregoing three manners areused as an overall solution, or the three solutions may be used as anoverall solution. For example, the first manner is independently used.In another case, another manner may be used, and is not limited to themethod provided in this embodiment of the present invention.Alternatively, the second manner is independently used. In another case,another manner may be used, and is not limited to the method provided inthis embodiment of the present invention. In addition, in theembodiments of the present invention, all parallel manners are similarto this case, and details are not described below again.

Optionally, the terminal device sends a second data packet on a seconduplink burst on condition that the second LBT succeeds, where the seconduplink burst is later than the first uplink burst.

Optionally, that the terminal device does not receive the firstindication information indicating the HARQ status after the first uplinkburst may be that the terminal device does not receive the firstindication information indicating the HARQ status after the first uplinkburst and before the second uplink burst, or may be that the terminaldevice does not receive, after the second reference time unitcorresponding to the first uplink burst and before the first referencetime unit, the first indication information indicating the HARQ status,or may be that the terminal device does not receive, within a first timethreshold starting from the second reference time unit corresponding tothe first uplink burst, the first indication information indicating theHARQ status.

The first uplink burst and the second uplink burst are bursts ofautonomous uplink (Autonomous UL, AUL) transmission. It should beunderstood that this description is applicable to all uplink bursts inthe embodiments of the present invention. The LBT previous to the secondLBT is previous LBT based on random backoff CCA. It should be understoodthat this description is also applicable to all LBT in the embodimentsof the present invention.

In the foregoing embodiment, a CWS is determined with reference to atime threshold, for example, a timer. After sending an uplink burst(referred to as the first uplink burst), if the terminal device does notreceive the indication information (referred to as the first indicationinformation) carrying the HARQ status, for example, the terminal devicedoes not receive the first indication information between the firstuplink burst and the second uplink burst, and the first reference timeunit exceeds the first time threshold corresponding to the first uplinkburst, to be specific, duration of a timer corresponding to the firstuplink burst, the terminal device performs channel listening afterincreasing the CWS corresponding to the second uplink burst. The timethreshold, for example, the timer, is set, so that the CWS is increasedwhen the first reference time unit exceeds the timer and no HARQ statusinformation is received, thereby avoiding that because there is a delayin feeding back the HARQ status information, the CWS is increased whenHARQ status information fed back by a network device is not receivedwithin a time interval (for example, a time interval less than thedelay) after one uplink burst. Therefore, it is avoided that a successrate of accessing a channel by the terminal device is reduced due to anexcessive increase of the CWS, so that the terminal device can moreproperly adapt to a channel status when performing AUL uplinktransmission.

According to a third aspect, an embodiment of the present inventionprovides a method for listening on an uplink channel. In the method, theterminal device sends a first data packet on a first uplink burst. Theterminal device performs first LBT, and sends a second data packet on asecond uplink burst after the first LBT succeeds. The second uplinkburst is later than the first uplink burst. The terminal devicedetermines a second contention window size CWS, and performs second LBTbased on the second CWS. The terminal device sends a third data packeton a third uplink burst on condition that the second LBT succeeds, wherethe third uplink burst is later than the second uplink burst. Aninterval between a first reference time unit and a second reference timeunit that corresponds to the first uplink burst is a first time length,and an interval between the first reference time unit and a secondreference time unit that corresponds to the second uplink burst is asecond time length. On condition that the second time length is greaterthan or equal to a first time threshold, and the first time length isgreater than or equal to the first time threshold, and the terminaldevice does not receive first indication information indicating an HARQstatus after the first uplink burst, the second CWS is a CWS increasedon a basis of a first CWS, and the first CWS is a CWS corresponding toLBT previous to the first LBT.

According to a fourth aspect, an embodiment of the present inventionprovides a wireless apparatus. The apparatus includes a processor, and amemory and a transceiver that are coupled to the processor.

The transceiver is configured to send a first data packet on a firstuplink burst. The processor is further configured to perform first LBT.The transceiver is further configured to send a second data packet on asecond uplink burst after the first LBT succeeds, where the seconduplink burst is later than the first uplink burst. The processor isfurther configured to: determine a second contention window size CWS,and perform second LBT based on the second CWS.

An interval between a first reference time unit and a second referencetime unit that corresponds to the first uplink burst is a first timelength, and an interval between the first reference time unit and asecond reference time unit that corresponds to the second uplink burstis a second time length. On condition that the second time length isgreater than or equal to a first time threshold, and the first timelength is greater than or equal to the first time threshold, and theterminal device does not receive first indication information indicatingan HARQ status after the first uplink burst, the second CWS is a CWSincreased on a basis of a first CWS, and the first CWS is a CWScorresponding to LBT previous to the first LBT.

The processor is further configured to control the terminal device senda third data packet on a third uplink burst on condition that the secondLBT succeeds, where the third uplink burst is later than the seconduplink burst.

In the third aspect and the fourth aspect, the first reference time unitexceeds the first time threshold corresponding to the first uplinkburst, that is, duration of a timer corresponding to the first uplinkburst, and the first reference time unit also exceeds duration of atimer corresponding to the second uplink burst. In addition, oncondition that no HARQ status information is received after the firstuplink burst, in other words, when the terminal device exceeds timerscorresponding to a plurality of uplink bursts and does not receive theHARQ status information, the terminal device increases the CWS onlyonce, thereby avoiding excessive penalty on the CWS when there are aplurality of times of expiration, and improving properness of adjustingthe CWS by the terminal device in an AUL scenario.

Optionally, the second CWS may be determined based on the secondindication information. When the second indication information is an ACKor a UL grant whose NDI is in a toggled state, the second CWS is lessthan the first CWS. When the second indication information is a NACK ora UL grant whose NDI is in a non-toggled state, the second CWS isgreater than the first CWS.

Optionally, the second reference time unit corresponding to the firstuplink burst is a time unit in the first uplink burst.

Optionally, the second reference time unit corresponding to the firstuplink burst is a time unit that has an interval of a third time lengthfrom a start time unit of the first uplink burst, and the secondreference time unit is after the start time unit of the first uplinkburst. Further, the second reference time unit corresponding to thefirst uplink burst may be the start time unit of the first uplink burst.

Optionally, the first CWS and the second CWS correspond to a same accesspriority.

According to a fifth aspect, an embodiment of the present inventionprovides a method for listening on an uplink channel by a terminaldevice. In the method, the terminal device sends a first data packet ona first uplink burst. The terminal device performs first LBT, and sendsa second data packet on a second uplink burst after the first LBTsucceeds, where the second uplink burst is later than the first uplinkburst. The terminal device determines a second contention window sizeCWS, and performs second LBT based on the second CWS. An intervalbetween a first reference time unit and a second reference time unitthat corresponds to the first uplink burst is a first time length, andan interval between the first reference time unit and a second referencetime unit that corresponds to the second uplink burst is a second timelength. The terminal device sends a third data packet on a third uplinkburst on condition that the second LBT succeeds, where the third uplinkburst is later than the second uplink burst.

In a first manner, on condition that the second time length is less thana first time threshold, and the first time length is greater than orequal to the first time threshold, and the terminal device does notreceive first indication information indicating an HARQ status after thefirst uplink burst, and further on condition that a first CWScorresponding to the first LBT is not increased compared with a thirdCWS, the second CWS is greater than a fourth CWS, where the fourth CWSis a CWS corresponding to LBT previous to the second LBT, and the thirdCWS is a CWS corresponding to LBT previous to the first LBT.

In a second manner, on condition that the second time length is lessthan a first time threshold, and the first time length is greater thanor equal to the first time threshold, and the terminal device does notreceive first indication information indicating an HARQ status after thefirst uplink burst, and further on condition that a first CWScorresponding to the first LBT is increased compared with the third CWS,the second CWS is equal to the fourth CWS, where the fourth CWS is a CWScorresponding to LBT previous to the second LBT, and the third CWS is aCWS corresponding to LBT previous to the first LBT.

According to a sixth aspect, an embodiment of the present inventionprovides a wireless apparatus. The apparatus includes a processor, and amemory and a transceiver that are coupled to the processor.

The transceiver is configured to send a first data packet on a firstuplink burst. The processor is configured to perform first LBT. Thetransceiver is further configured to send a second data packet on asecond uplink burst after the first LBT succeeds, where the seconduplink burst is later than the first uplink burst. The processor isfurther configured to: determine a second contention window size CWS,and perform second LBT based on the second CWS. An interval between afirst reference time unit and a second reference time unit thatcorresponds to the first uplink burst is a first time length, and aninterval between the first reference time unit and a second referencetime unit that corresponds to the second uplink burst is a second timelength.

In a first manner, on condition that the second time length is less thana first time threshold, and the first time length is greater than orequal to the first time threshold, and the wireless apparatus does notreceive first indication information indicating an HARQ status after thefirst uplink burst, and further on condition that a first CWScorresponding to the first LBT is not increased compared with a thirdCWS, the second CWS is greater than a fourth CWS, where the fourth CWSis a CWS corresponding to LBT previous to the second LBT, and the thirdCWS is a CWS corresponding to LBT previous to the first LBT.

In a second manner, on condition that the second time length is lessthan a first time threshold, and the first time length is greater thanor equal to the first time threshold, and the wireless apparatus doesnot receive first indication information indicating an HARQ status afterthe first uplink burst, and further on condition that a first CWScorresponding to the first LBT is increased compared with the third CWS,the second CWS is equal to the fourth CWS, where the fourth CWS is a CWScorresponding to LBT previous to the second LBT, and the third CWS is aCWS corresponding to LBT previous to the first LBT; and

the transceiver is further configured to send a third data packet on athird uplink burst on condition that the second LBT succeeds, where thethird uplink burst is later than the second uplink burst.

In the foregoing embodiment, on condition that the third uplink burstexceeds a timer corresponding to the first uplink burst, in other words,the first time length is greater than or equal to the first timethreshold, when there is the second uplink burst between the firstuplink burst and the third uplink burst, on condition that the first CWScorresponding to the first LBT is increased compared with the third CWS,the third CWS is a CWS corresponding to LBT previous to the first LBT,in other words, a CWS corresponding to the second uplink burst is a CWSthat has been increased compared with the CWS corresponding to theprevious LBT. In addition, if the third uplink burst does not exceed thetimer corresponding to the second uplink burst, in other words, thesecond time length is less than the first time threshold, the terminaldevice does not increase the second CWS, that is, the second CWS isequal to the fourth CWS. Optionally, the terminal device restarts a newtimer for the second uplink burst on which the CWS has been adjusted,and determines, based on a receiving status of an HARQ status and thetime interval between the second uplink burst and the third uplinkburst, the CWS corresponding to the third uplink burst.

According to the method provided in this embodiment, on condition thatthe HARQ status information is not received after the first uplinkburst, the terminal device has increased the CWS corresponding to thesecond uplink burst between the first uplink burst and the third uplinkburst, and the first reference time unit does not exceed timer durationof the second uplink burst, the terminal device does not increase,because the third uplink burst exceeds timer duration corresponding tothe first uplink burst, the CWS corresponding to the third uplink burst,but keeps the CWS corresponding to the third uplink burst unchanged.Compared with the method in which the terminal device increases the CWSprovided that the first reference time unit exceeds the timer duration,this embodiment improves properness of adjusting the CWS by the terminaldevice in the AUL scenario.

It should be noted that the first manner and the second manner hereinmay be used as an overall solution, or may be used as independentsolutions.

Optionally, the second reference time unit corresponding to the firstuplink burst is a time unit in the first uplink burst; or the secondreference time unit corresponding to the first uplink burst is a timeunit that has an interval of a third time length from a start time unitof the first uplink burst, and the second reference time unit is afterthe start time unit of the first uplink burst; and

the second reference time unit corresponding to the second uplink burstis a time unit in the second uplink burst; or the second reference timeunit corresponding to the second uplink burst is a time unit that has aninterval of a third time length from a start time unit of the seconduplink burst, and the second reference time unit is after the start timeunit of the first uplink burst.

Further, the second reference time unit corresponding to the firstuplink burst may be different from the second reference time unitcorresponding to the second uplink burst.

Optionally, the second reference time unit corresponding to the firstuplink burst is the start time unit of the first uplink burst; or thesecond reference time unit corresponding to the second uplink burst isthe start time unit of the second uplink burst.

Optionally, the second CWS and the third CWS correspond to a same accesspriority, and the first CWS and the fourth CWS correspond to a sameaccess priority.

Optionally, in the foregoing aspects, the first reference time unit is atime unit in which the terminal device determines the second CWS.

Further, embodiments of the foregoing aspects may further include:sending a second data packet on a second uplink burst on condition thatthe second LBT succeeds, where the second uplink burst is later than thefirst uplink burst.

Optionally, the first reference time unit is a start time unit of thesecond uplink burst.

Optionally, the LBT previous to the second LBT is the same as the firstLBT.

Further, the second time length may be predefined or received from anetwork device.

Optionally, the third time length may be related to a delay of feedingback an HARQ status by the network device.

Optionally, the second CWS and the first CWS correspond to a same accesspriority.

Optionally, the determining, by the terminal device, a second CWSfurther includes: on condition that the first time length is greaterthan or equal to the first time threshold, and the terminal device doesnot receive, within a time after the first uplink burst and before thesecond uplink burst, the first indication information indicating theHARQ status, and the second uplink burst is an uplink burst immediatelyafter a third reference time unit corresponding to the first uplinkburst, the second CWS is greater than the first CWS, the first CWS is aCWS corresponding to LBT previous to the second LBT, the third referencetime unit corresponding to the first uplink burst is later than thesecond reference time unit corresponding to the first uplink burst, anda time interval between the third reference time unit corresponding tothe first uplink burst and the second reference time unit correspondingto the first uplink burst is the first time threshold.

Optionally, in this embodiment of the present invention, that the secondCWS is greater than the first CWS may mean that in a CWS set, the secondCWS is a next-level CWS of the first CWS, that is, a smallest CWS thatis greater than the first CWS and that is in the CWS set.

For example, CWS values available for the terminal device form a CWSset. When increasing a CWS, the terminal device increases the CWS to anext higher value in the CWS set. For example, the CWS set may be {3,7}, {7, 15}, or {15, 31, 63, 127, 255, 511, 1023}.

Optionally, when decreasing the CWS, the terminal device decreases theCWS to a smallest value in the CWS set.

According to a seventh aspect, a communications apparatus is provided.The communications apparatus is configured to perform functions ofbehaviors of the terminal device in the foregoing method in actuality.These functions may be implemented by hardware, or may be implemented byhardware executing corresponding software. The hardware or the softwareincludes one or more units corresponding to the functions.

According to an eighth aspect, a computer storage medium including aninstruction is provided. When the instruction is run on a computer, thecomputer is enabled to perform functions of behaviors of the terminaldevice in the foregoing method in actuality.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of a communications system to which anembodiment of the present invention applies;

FIG. 2 is a schematic communication diagram of a method for listening onan uplink channel according to an embodiment of the present invention;

FIG. 3 to FIG. 7 are sequence diagrams of a method for listening on anuplink channel according to an embodiment of the present invention;

FIG. 8 is a schematic communication diagram of another method forlistening on an uplink channel according to an embodiment of the presentinvention;

FIG. 9 and FIG. 10 are sequence diagrams of another method for listeningon an uplink channel according to an embodiment of the presentinvention;

FIG. 11 is a sequence diagram of still another method for listening onan uplink channel according to an embodiment of the present invention;and

FIG. 12 is a schematic block diagram of an apparatus for listening on anuplink channel according to an embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes technical solutions in embodiments of thepresent invention with reference to the accompanying drawings.

Terminologies such as “component”, “module”, and “system” used in thisspecification are used to indicate computer-related entities, hardware,firmware, combinations of hardware and software, software, or softwarebeing executed. For example, a component may be, but is not limited to,a process that runs on a processor, a processor, an object, anexecutable file, a thread of execution, a program, and/or a computer. Asshown in figures, both a computing device and an application that runson a computing device may be components. One or more components mayreside within a process and/or a thread of execution, and a componentmay be located on one computer and/or distributed between two or morecomputers. In addition, these components may be executed from variouscomputer-readable media that store various data structures. For example,the components may communicate by using a local and/or remote processand according to, for example, a signal having one or more data packets(for example, data from two components interacting with anothercomponent in a local system, a distributed system, and/or across anetwork such as the Internet interacting with other systems by using thesignal).

It should be understood that the present invention is applicable to awireless cellular communications network system using an unlicensedspectrum for communication, for example, a licensed assisted access(Licensed assisted access, LAA) system of long term evolution (Long TermEvolution, LTE), an enhanced licensed assisted access (Enhanced LicensedAssisted Access, eLAA) system, a further enhanced licensed assistedaccess (Further Enhanced Licensed Assisted Access, FeLAA) system, acommunications system using an unlicensed spectrum in a 5Gcommunications system, and a MulteFire system independently working inan unlicensed spectrum, and a communications system using an unlicensedspectrum in a future mobile communications network.

FIG. 1 is a schematic diagram of a communications system according to anembodiment of the present invention. As shown in FIG. 1, thecommunications system 100 includes a network device 102. The networkdevice 102 may include a plurality of antennas, for example, antennas104, 106, 108, 110, 112, and 114. In addition, the network device 102may additionally include a transmitter chain and a receiver chain. Aperson of ordinary skill in the art may understand that both thetransmitter chain and the receiver chain may include a plurality ofcomponents (for example, a processor, a modulator, a multiplexer, ademodulator, a demultiplexer, or an antenna) related to signal sendingand receiving. The network device 102 may communicate with a pluralityof terminal devices (such as a terminal device 116 and a terminal device122). However, it may be understood that the network device 102 maycommunicate with any quantity of terminal devices that are similar tothe terminal device 116 or 122.

As shown in FIG. 1, the terminal device 116 communicates with thenetwork device 102. The network device 102 sends information to theterminal device 116 over a downlink 118, and receives information fromthe terminal device 116 over an uplink 120. In addition, the terminaldevice 122 communicates with the network device 102. The network device102 sends information to the terminal device 122 over a downlink 124,and receives information from the terminal device 122 over an uplink126.

For example, on an unlicensed frequency band, the downlink 118 and theuplink 120 may use a same frequency band, and the downlink 124 and theuplink 126 may use a same frequency band.

In addition, the communications system 100 may be a public land mobilenetwork (Public Land Mobile Network, PLMN), a D2D network, an M2Mnetwork, or another network. FIG. 1 is only an example of a simplifiedschematic diagram. The network may further include another networkdevice not shown in FIG. 1.

The embodiments of the present invention describe the embodiments withreference to a terminal device. The terminal device may also be referredto as user equipment (User Equipment, UE), a mobile station (MobileStation, MS), a mobile terminal (Mobile Terminal), or the like. Theterminal device may communicate with one or more core networks by usinga radio access network (Radio Access Network, RAN). For example, theterminal device is a device that has a wireless transceiver function,may be deployed on land, including being deployed indoor or outdoor, andmay be handheld or vehicle-mounted; may be deployed on water (such asships); or may be deployed in the air (such as airplanes, balloons, andsatellites). The terminal device may be a mobile phone (mobile phone), atablet computer (Pad), a computer with a wireless transceiver function,a virtual reality (Virtual Reality, VR) terminal device, an augmentedreality (Augmented Reality, AR) terminal device, a wireless terminal inindustrial control (industrial control), a wireless terminal in selfdriving (self driving), a wireless terminal in remote medical (remotemedical), a wireless terminal in smart grid (smart grid), a wirelessterminal in transportation safety (transportation safety), a wirelessterminal in a smart city (smart city), a wireless terminal in a smarthome (smart home), or the like.

In addition, a network device (for example, the network device 201) inthis embodiment of the present invention is an apparatus that isdeployed in a radio access network and that is configured to provide awireless communication function for a terminal device. The networkdevice may include various forms of macro base stations, micro basestations (also referred to as small cells), relay stations, accesspoints, and the like. The network device may be a base transceiverstation (Base Transceiver Station, BTS) in GSM or CDMA, may be a NodeB(NodeB, NB) in WCDMA, may be an evolved NodeB (evolved Node B, eNB, ore-NodeB) in LTE or eLTE, or may be a next-generation mobile network, forexample, a base station gNB ((next) generation NodeB) in 5G (fifthgeneration).

A time-frequency resource used in the communications system 100 forwireless communication is described in detail below.

In the embodiments of the present invention, time domain resources usedfor transmitting information by the network device and the terminaldevice may be divided into a plurality of time units in time domain.

In addition, in this embodiment of the present invention, the pluralityof time units may be consecutive, or a preset interval is set betweensome adjacent time units. This is not specially limited in thisembodiment of the present invention.

In the embodiments of the present invention, the time unit may include atime unit used for uplink information (for example, uplink data)transmission and/or downlink information (for example, downlink data)transmission.

In the embodiments of the present invention, a length of one time unitmay be randomly set. This is not specially limited in the embodiments ofthe present invention.

For example, one time unit may include one or more subframes; or

one time unit may include one or more slots; or

one time unit may include one or more symbols; or

one time unit may include one or more TTIs (Transmission Time Interval,TTI); or

one time unit may include one or more short transmission time intervals(short Transmission Time Interval, sTTI).

In this embodiment of the present invention, a time-frequency resourceused in the communications system 100 for wireless communication may bedivided into a plurality of TTIs in time domain. The TTI is a commonlyused parameter in a current communications system (for example, an LTEsystem), and is a scheduling unit for scheduling informationtransmission on a radio link.

It should be understood that, in this embodiment of the presentinvention, the TTI may be a 1-ms TTI, or may be referred to as asubframe with a length of 1 ms, or may be an sTTI shorter than 1 ms, ormay be referred to as a mini-slot (mini-slot). A length of a time domainresource occupied by the sTTI is shorter than that of the 1-ms TTI. Inother words, when a TTI corresponding to a data channel is an sTTI, alength of a time domain resource occupied by the terminal device is lessthan 1 ms. For uplink transmission, a TTI is a time domain granularityfor uplink resource allocation or uplink transmission, or a TTI is aminimum time domain unit for performing uplink transmission by theterminal device.

Due to a latency-sensitive service requirement, a structure of a shorterTTI frame needs to be introduced in a physical layer, to further shortenthe scheduling interval and improve user experience. For example, alength of a TTI in the LTE system may be shortened from 1 ms to a rangeof 1 symbol (symbol) to 1 slot (including 7 symbols). The foregoingsymbol may be an orthogonal frequency division multiplexing (OrthogonalFrequency Division Multiplexing, OFDM) symbol or a singlecarrier—frequency division multiple access (Single Carrier FrequencyDivision Multiple Access, SC-FDMA) symbol in the LTE system, or may be asymbol in another communications system. For another example, a TTIlength in a 5G communications system is also less than 1 ms.

A TTI having a length less than 1 ms can be referred to as an sTTI. Forexample, in the LTE system, a length of the sTTI may be any length ofone symbol to seven symbols, or a length of the sTTI may be acombination of at least two different lengths in one symbol to sevensymbols. For example, 1 ms includes six sTTIs, and lengths of the sTTIsmay be respectively three symbols, two symbols, two symbols, twosymbols, two symbols, and three symbols. Alternatively, 1 ms includesfour sTTIs, and lengths of the sTTIs may be respectively three symbols,four symbols, three symbols, and four symbols, or may be a combinationof other different lengths.

In the embodiments of the present invention, a TTI (for example, a TTIwhose length is 1 ms or longer than 1 ms) and an sTTI that are specifiedin the prior art (for example, the LTE system) may be collectivelyreferred to as a TTI. In addition, in the embodiments of the presentinvention, a length of a TTI may be changed based on an actualrequirement.

It should be understood that the foregoing listed structure of the timeunit is merely an example for description. This embodiment of thepresent invention is not specially limited, and a structure of the timeunit may be randomly changed based on an actual requirement. Forexample, for an LTE system that does not support the sTTI, one time unitmay be one subframe (Subframe). For another example, for an LTE systemthat supports the sTTI, one time unit may include one sTTI, one timeunit may include one slot (Slot), one time unit may include one or more(for example, a positive integer less than 7 or a positive integer lessthan 6) symbols, or one time unit may be one subframe.

It should be understood that when one time unit includes at least onesymbol, any one of the at least one symbol may be a complete symbol ormay be a part of a symbol. The part of the symbol means that a deviceoccupies a part of a time domain resource of the symbol to sendinformation, and the remaining part is not used to send information oris reserved as clear.

It should be noted that, in the embodiments of the present invention, alength (or information transmission duration) that is of a time unit andthat is used to transmit information may be 1 ms, or may be less than 1ms.

In this embodiment of the present invention, a frequency domain resourceused by the communications system 100 includes an unlicensed frequencyband. It should be understood that the present invention is applicableto a wireless cellular communications network system using an unlicensedspectrum for communication, for example, a licensed assisted access(Licensed Assisted Access, LAA) system of long term evolution (Long TermEvolution, LTE), an enhanced licensed assisted access (Enhanced LicensedAssisted Access, eLAA) system, a further enhanced licensed assistedaccess (Further Enhanced Licensed Assisted Access, FeLAA) system, acommunications system using an unlicensed spectrum in a 5Gcommunications system, or a MulteFire system independently working in anunlicensed spectrum. The simplified communications system 100 is used asan example in this embodiment of the present invention, and does notconstitute a limitation on the technical solutions provided in theembodiments of the present invention. A person of ordinary skill in theart may know that with evolution of a network architecture and emergenceof a new service scenario, the technical solutions provided in theembodiments of the present invention are also applicable to a similartechnical problem.

To implement fair coexistence with network devices and terminal devicesof different operators and inter-RAT such as Wi-Fi radio nodes on anunlicensed spectrum, a system working on the unlicensed spectrum, suchas an LAA/eLAA/Multefire system, needs to use a listen-before-talk(Listen-Before-Talk, LBT) channel access mechanism. Before the networkdevice performs downlink transmission or before the terminal deviceperforms uplink transmission, the network device or the terminal deviceneeds to listen on a channel, and occupies the channel for transmissionafter detecting that the channel is clear. If a sending node detectsthat a channel is clear before the sending node wants to occupy aresource, it is referred to as an LBT success; otherwise, it is referredto as an LBT failure.

An LBT procedure that is used by a sending node (a network device or aterminal device) to occupy a channel before transmission includes arandom backoff clear channel assessment (Clear Channel Assessment, CCA)process. That the network device performs downlink transmission is usedas an example. A specific procedure of the CCA process may be describedas follows: The network device evenly and randomly generates a backoffcounter N between 0 and a contention window size (Contention WindowSize, CWS), and performs listening at a granularity of listening slot(CCA slot, for example, duration of 9 μs). If the network device detectsthat a channel is clear within the listening slot, the network devicedecreases the backoff counter by 1; or if the network device detectsthat a channel is busy, the network device suspends the backoff counter,that is, the backoff counter N remains unchanged in the time in whichthe channel is busy, until the network device detects that the channelis clear. When the backoff counter is decreased to 0 (which is referredto as backoff counter zeroization), it is referred to as an LBT success,and the network device may immediately occupy the channel to senddownlink information. In addition, after the backoff counter is reset tozero, the network device may wait for a period of time instead ofimmediately sending the downlink information. After the waiting ends,the network device performs listening on an additional slot before amoment at which the downlink information needs to be sent. If thenetwork device listens and detects, in the additional slot, that achannel is clear, it is considered that the channel listening succeeds,and the network device may immediately send the information. If thebackoff counter is not reset to zero before the downlink information issent, or the additional listening slot is busy, it is referred to as achannel listening failure. The network device uses a dynamicallyadjusted CWS in a downlink transmission process. The network devicedynamically adjusts the CWS for downlink transmission based on an HARQstatus that is fed back by the terminal device for a downlink referencesubframe. When a proportion of negative acknowledgement (negativeacknowledgement, NACK) feedbacks corresponding to the downlink referencesubframe is relatively large, the network device increases the CWS, andperforms channel listening in next LBT by using the increased CWS, toavoid a collision with a surrounding contention node by prolonging alistening time, thereby implementing fair coexistence. When a proportionof acknowledgement (acknowledgement, ACK) feedbacks is relatively large,the network device decreases the CWS, to reduce a listening time forfaster channel access.

The uplink burst in this embodiment of the present invention may includeone or more time units that are consecutive in time. For a concept ofthe time unit, refer to the foregoing description. Specifically, on anunlicensed spectrum, after completing successful LBT, a sending deviceis allowed to continuously send information for a maximum period of timeon the spectrum. This period of time is referred to as a maximum channeloccupancy time. Within the maximum channel occupancy time, the sendingdevice does not need to interrupt sending to re-listen on a channel.Once the maximum channel occupancy time is exceeded, the sending deviceneeds to stop sending to re-listen on the channel, and can performsending again only after the LBT succeeds again. The uplink burst in thepresent invention is one or more time units in which the terminal devicecontinuously performs sending after successfully completing LBT once,and total duration of the one or more time units does not exceed themaximum channel occupancy time. If the terminal device needs to continueto send the uplink information after one uplink burst interruption, theterminal device needs to listen on the channel again. A next uplinkburst can be started only after LBT succeeds again. Optionally, theterminal device may send one or a combination of uplink data, uplinkcontrol information, or an uplink reference signal in the uplink burst.Optionally, two consecutive time units in the uplink burst may beinconsecutive in time. For example, there may be a gap between twoadjacent time units included in the uplink burst. For example, theuplink burst does not occupy time domain resources of start symbolsand/or end symbols of some time units.

In a further enhanced licensed-assisted access (Further enhancedLicensed-Assisted Access, FeLAA) system and a Multefire 1.1 system thatare introduced in Release 15, a grant-free uplink (Grant free Uplink orGrantless Uplink, GUL) transmission mechanism, or referred to as anautonomous uplink (Autonomous UL, AUL) transmission mechanism, isintroduced. In this way, the terminal device does not need to send an SRor wait for a UL grant, and channel listening for the SR and the ULgrant is removed. Instead, the terminal device may directly send uplinkdata on a reserved AUL resource after LBT succeeds. The AUL transmissionmechanism described in this embodiment of the present invention includesat least one of the following features:

1. No scheduling request (Scheduling Request, SR) needs to be sent tothe network device for the uplink information of the terminal device,and the network device does not need to dynamically schedule the uplinkinformation. Instead, the terminal device independently determines tosend the uplink information.

2. Different from scheduling-based uplink (Scheduling based Uplink, SUL)transmission, the network device semi-statically or semi-persistentlyconfigures, for the terminal device, the AUL radio resource used for AULtransmission, including a time domain resource and a frequency domainresource. Specifically, the AUL radio resource is configured for theterminal device by using semi-persistent RRC signaling and/orsemi-persistent DCI signaling. Specifically, the AUL time domainresource is periodic, or the AUL time domain resource is a persistenttime domain resource, and the SUL-based uplink information takes effectonly for a limited quantity of time units.

3. The terminal device reports grant-free uplink control information(also called as Autonomous Uplink Control Information, A-UCI) whensending AUL uplink information, where the A-UCI is control informationcorresponding to the uplink data. The A-UCI includes at least one ofHARQ process number information of an HARQ process corresponding to theuplink information, new data indicator (New Data Indicator, NDI)information, redundancy version (Redundancy Version, RV) informationcorresponding to the uplink information, and user identifier (denoted asa UE ID) information of the terminal device.

Before performing uplink transmission, the terminal device also needs toperform an LBT procedure. The LBT procedure used to occupy an uplinkchannel also includes a random backoff CCA procedure, which is referredto as a random backoff CCA-based LBT. Similar to downlink LBT, theterminal device evenly and randomly generates a backoff counter Nbetween 0 and a CWS, and performs channel listening on a carrier at agranularity of listening slot (for example, duration of 9 μs). If theterminal device detects that the channel is clear within the listeningslot, the terminal device decreases the backoff counter by 1. If theterminal device detects that the channel is busy within the listeningslot, the terminal device suspends the backoff counter, that is, thebackoff counter N remains unchanged within the time for which thechannel is busy, and does not count the backoff counter again until theterminal device detects that the channel is clear. When the backoffcounter is reset to 0, it is considered that the channel listeningsucceeds, and the terminal device may immediately occupy the channel tosend the uplink information. In addition, after the backoff counter isreset to zero, the terminal device may wait for a period of time insteadof immediately sending the uplink information. After the waiting ends,the terminal device performs listening on an additional slot before amoment at which the uplink information needs to be sent. If the terminaldevice listens and detects, in the additional slot, that a channel isclear, it is considered that the channel listening succeeds, and theterminal device may immediately send the information. If the backoffcounter is not reset to zero before the uplink information is sent, orthe additional listening slot is busy, it is referred to as a channellistening failure. Similar to downlink, when performing an LBT procedurethat occupies a channel, the terminal device also uses a mechanism ofdynamically adjusting a CWS. The terminal device dynamically adjusts aCWS for an uplink burst based on an HARQ status of an uplink referencesubframe. When the HARQ status of the uplink reference subframe isacknowledged, the terminal device decreases the CWS. Otherwise, theterminal device increases the CWS.

It should be understood that, for a terminal device that supports AULtransmission, receiving HARQ status information includes the followingcases:

1. The terminal device receives an uplink grant (uplink grant, UL grant)sent by the network device, and the network device indicates a receivingstatus of AUL data, that is, the HARQ status, while scheduling theterminal device. For example, on condition that the network device doesnot correctly receive the AUL data, but correctly identifies, bydetecting sequence information (for example, a sequence of an uplinkdemodulation reference signal) of AUL transmission, the terminal deviceto which the AUL data belongs, the network device sends a UL grant toschedule the terminal device to perform retransmission on an SULresource. If NDI in the UL grant is not toggled compared with NDIcorresponding to the AUL data, that is, an NDI value does not change, itindicates that the AUL data is not correctly received. This isequivalent to a NACK feedback for the AUL data. In this case, theterminal device increases the CWS. On condition that the NDI in the ULgrant is toggled compared with the NDI corresponding to the AUL data,which is equivalent to an ACK feedback of the AUL data, the terminaldevice decreases the CWS.

2. The terminal device receives the HARQ-ACK feedback information sentby the network device, to indicate whether previous transmissionperformed by the terminal device by using an HARQ process number iscorrectly received. For example, if previous transmission performedbased on an HARQ process number is correctly received, the networkdevice sends an ACK to the terminal device; or if previous transmissionperformed based on an HARQ process number is not correctly received, thenetwork device sends a NACK to the terminal device. Further, theHARQ-ACK feedback information may be a plurality of pieces of HARQ-ACKinformation respectively corresponding to a plurality of AUL HARQprocesses. Therefore, the HARQ-ACK feedback information may be carriedon an independent downlink control channel. The downlink control channelgenerally does not need to include resource allocation information, butmay include information such as power control information. Optionally,the HARQ-ACK feedback information may alternatively include resourceallocation information, power control information, and the like.

It should be understood that CWS values available for the terminaldevice form a CWS set. When increasing a CWS, the terminal deviceincreases the CWS to a next higher value in the CWS set. When reducing aCWS, the terminal device decreases the CWS to a smallest value in theCWS set. For example, the CWS set may be {3, 7}, {7, 15}, or {15, 31,63, 127, 255, 511, 1023}.

In this embodiment, increasing a CWS may be increasing a CWS to a nextlevel, for example, increasing 3 to 7, or increasing 63 to 127.

For grant-free uplink transmission, the network device does not know inadvance that the terminal device sends the AUL transmission. Therefore,after the terminal device sends the AUL transmission, when the networkdevice does not correctly receive the AUL transmission from the terminaldevice and does not identify the terminal device corresponding to theAUL transmission, the network device cannot feed back corresponding HARQstatus (a UL grant, an HARQ-ACK feedback, or the like) information tothe terminal device. The terminal device corresponding to the AULtransmission may not be identified due to a conflict caused because aplurality of terminal devices simultaneously perform AUL transmission ona reserved resource. Consequently, the network device does not identifyan uplink sequence (for example, an uplink demodulation referencesignal) sent by any terminal device, or even if the uplink sequence isidentified, the network device cannot identify the terminal device onlyby using the uplink sequence. For example, the network device may havenot correctly received or decoded uplink control information, and theuplink control information carries identification information of theterminal device. In the foregoing case, the terminal device cannotreceive any HARQ status information after the AUL transmission, andcannot adjust an uplink CWS based on the HARQ status information fedback by the network device in the prior art, to adapt to a channelstatus.

In another possible case, the network device identifies, through uplinksequence detection, the terminal device that performs AUL transmission,or correctly decodes uplink control information and uplink datainformation. However, considering system overheads, the network devicedoes not immediately feed back HARQ status information to the AULterminal device, but waits for the terminal device to perform AULtransmission for a plurality of times. Then, HARQ-ACK feedbackinformation corresponding to HARQ processes of a plurality of AULtransmissions is simultaneously fed back through one downlinktransmission. In this case, that the HARQ status information is notreceived within a period of time after an uplink burst does not indicatethat an uplink channel status becomes poor. If the terminal deviceincreases the CWS in this case, the terminal device possibly cannotoccupy a channel within a longer time. Consequently, channel resourceutilization may be reduced, and transmission efficiency of the terminaldevice may be reduced.

To resolve the foregoing problem, an embodiment of the present inventionprovides a method for listening on an uplink channel, to properly adjusta CWS when a terminal device does not receive HARQ status information ina scenario of grant-free transmission on an unlicensed spectrum, toadapt to a channel status and avoid excessive penalty on an uplink CWS.

The method provided in the embodiments of the present invention isdescribed in detail with reference to FIG. 2 to FIG. 9. FIG. 2 is aschematic diagram of a method for listening on a channel according to anembodiment of the present invention.

Step 210: A terminal device performs first LBT.

The operation in this step may be implemented by a modem processor 124of a terminal device in FIG. 12.

Step 220: The terminal device sends a first data packet on a firstuplink burst after the first LBT succeeds.

It should be understood that one uplink burst is a time-frequencyresource occupied for sending a data packet after the terminal devicesuccessfully performs random backoff CCA-based LBT once. The uplinkburst includes at least one time unit, and the at least one time unitmay be consecutive in time. For example, TTIs or subframe sequencenumbers included in the uplink burst are consecutive. Alternatively, theat least one time unit may be inconsecutive in time. There may be aninterval between any two adjacent time units included in the uplinkburst. For example, the uplink burst does not occupy a time domainresource at a start or an end of the time unit. This is not limited inthis embodiment of the present invention.

It should be further understood that the terminal device sendsgrant-free AUL uplink information in the first uplink burst, or sends apart of AUL uplink information in the first burst. The foregoingdescription is also applicable to another uplink burst in thisembodiment of the present invention, for example, a second uplink burstand a third uplink burst. Any two different uplink bursts areinconsecutive in time, for example, a first uplink burst and a seconduplink burst in FIG. 2.

The sending action in this step may be implemented by a transceiver 121of the terminal device in FIG. 12. Certainly, the action mayalternatively be implemented by the modem processor 124 of the terminaldevice in FIG. 12 by controlling the transceiver 121.

Step 230: The terminal device determines a second contention window sizeCWS.

In a first manner, on condition that a first time length is greater thanor equal to a first time threshold, and the terminal device does notreceive first indication information indicating an HARQ status after thefirst uplink burst, the second CWS is greater than a first CWS.

The operation in this step may be implemented by the modem processor 124of the terminal device in FIG. 12.

Optionally, the terminal device sends a second data packet on a seconduplink burst on condition that a second LBT succeeds, where the seconduplink burst is later than the first uplink burst.

Optionally, the first indication information indicating the HARQ statusincludes HARQ status information corresponding to AUL transmission andSUL transmission, or the first indication information indicating theHARQ status includes HARQ status information corresponding to AULtransmission but does not include HARQ status information correspondingto SUL transmission. It should be understood that the foregoingdescription of the first indication information indicating the HARQstatus is also applicable to another embodiment of the presentinvention.

In this embodiment of the present invention, a timer is introduced todetermine a CWS. A second reference time unit corresponding to the firstuplink burst is a start point of the timer corresponding to the firstuplink burst. Specifically, a start moment of the timer is an end momentor a start moment of the second reference time unit, and a length of thetimer is the first time threshold. In this embodiment of the presentinvention, an example in which the start moment of the timer is the endmoment of the second reference time unit is used. It should beunderstood that the foregoing description of the start point and thelength of the timer is also applicable to a timer corresponding toanother burst in this embodiment of the present invention. For example,in another embodiment of the present invention, a second reference timeunit corresponding to the second uplink burst is a start point of thetimer corresponding to the second uplink burst.

It should be noted that there are the following possible cases for thesecond reference time unit corresponding to the first uplink burst:

Case 1

The second reference time unit corresponding to the first uplink burstis a time unit in the first uplink burst, for example, a subframe or aTTI. Optionally, the second reference time unit corresponding to thefirst uplink burst is an end subframe or TTI in the first uplink burst.Specifically, a start point of a timer corresponding to the first uplinkburst is an end moment of the first uplink burst, as shown in (a) inFIG. 3. Optionally, the second reference time unit corresponding to thefirst uplink burst is an earliest subframe or TTI in the first uplinkburst. Specifically, a start point of a timer corresponding to the firstuplink burst is an end moment of the earliest subframe or TTI in thefirst uplink burst, as shown in (b) in FIG. 3.

Case 2

The second reference time unit corresponding to the first uplink burstis a time unit at an interval of a third time length after a target timeunit in the first uplink burst. Optionally, the target time unit in thefirst uplink burst is the first time unit in the first uplink burst. Forexample, the target time unit is the first subframe or TTI in the firstuplink burst. Specifically, a start point of a timer corresponding tothe first uplink burst is a moment at a third time length after thefirst subframe or TTI in the first uplink burst, as shown in (c) in FIG.3.

Optionally, a second time length may be defined in a protocol or aregulation, for example, may be preset in the terminal device.Alternatively, the second time length may be configured by a networkdevice by using higher layer signaling or notified by a network deviceby using physical layer signaling. Further, the second time length maybe an HARQ status information feedback delay or greater than thefeedback delay. Specifically, after receiving uplink data information,the network device feeds back the HARQ status information of the datainformation with a delay. For example, HARQ status informationcorresponding to data information in a time unit #n may be first fedback in a time unit #n+k. In this case, the HARQ status informationfeedback delay is referred to as k time units. Optionally, the secondtime length may be k subframes or TTIs. For example, the second timelength may be k=4 subframes or TTIs.

It should be understood that two possible cases of the second referencetime unit corresponding to the first uplink burst are also applicable toa second reference time unit corresponding to another uplink burst inthis embodiment of the present invention, for example, the secondreference time unit corresponding to the second uplink burst. Detailsare not described below again.

In a possible design, a first reference time unit is a time unit inwhich the terminal device determines the second CWS. For example, if theterminal device determines the second CWS in a TTI, the first referencetime unit is the TTI or a start time unit of the second uplink burst.For example, the start time unit may be a start time unit determined bythe terminal device based on a time sequence relationship. The followingseparately describes two possibilities of the first reference time unit:

Possibility 1: The first reference time unit is a time unit in which theterminal device determines the second CWS. In this case, the first timelength is a time length from the start point of the timer correspondingto the first uplink burst to the time unit in which the terminal devicedetermines the second CWS. In this possibility, that the first timelength is greater than the first time threshold indicates that the timeunit in which the terminal device determines the second CWS exceeds theend point of the timer corresponding to the first uplink burst, and thisis referred to as that the first reference time unit exceeds the timer.

It should be understood that the time unit in which the terminal devicedetermines the second CWS is a time unit before the terminal deviceperforms the second LBT. For example, the terminal device needs to senduplink AUL information, and needs to determine, before the second LBToccupies an unlicensed channel, the second CWS corresponding to thesecond LBT.

Optionally, in the time unit in which the terminal device determines thesecond CWS, the terminal device does not need to send uplink AULinformation. For example, on condition that the timer corresponding tothe first uplink burst expires and no HARQ status information isreceived, the terminal device immediately increases a CWS, that is,determines the second CWS. After a period of time, when the terminaldevice needs to send uplink AUL information, the terminal deviceperforms the second LBT based on the second CWS, and sends uplinkinformation in the second uplink burst on condition that the second LBTsucceeds.

Possibility 2: The first reference time unit is a start time unit of thesecond uplink burst. For example, the start time unit may be a starttime unit determined by the terminal device based on a time sequencerelationship. Optionally, the start time unit of the second uplink burstmay be the first (earliest) subframe or TTI in the second uplink burst.In this possibility, that the first time length is greater than thefirst time threshold indicates that the start time unit or the startmoment of the second uplink burst exceeds the end point of the timercorresponding to the first uplink burst, and this is referred to as thatthe first reference time unit exceeds the timer.

It should be understood that the two possible cases of the firstreference time unit are also applicable to a first reference time unitcorresponding to another uplink burst in this embodiment of the presentinvention, for example, a first reference time unit corresponding to athird uplink burst. Details are not described below again.

An interval between the first reference time unit and the secondreference time unit that corresponds to the first uplink burst is thefirst time length, that is, an interval between the first reference timeunit and the start point of the timer corresponding to the first uplinkburst is the first time length.

On condition that the first time length is greater than or equal to thefirst time threshold, and the terminal device does not receive firstindication information indicating an HARQ status after the first uplinkburst, the second CWS is greater than a first CWS, where the first CWSis a CWS corresponding to LBT previous to the second LBT. As shown (a),(b), and (c) in FIG. 2, the terminal device does not receive the firstindication information indicating the HARQ status after the first uplinkburst, and the first reference time unit corresponding to the seconduplink burst exceeds a timer T1 corresponding to the first uplink burst.It should be understood that, as described above, the first indicationinformation indicating the HARQ status includes at least one of HARQ-ACKfeedback information and a UL grant. In this case, the terminal deviceincreases the CWS. In other words, the second CWS is greater than thefirst CWS, and the first CWS is a CWS corresponding to LBT previous tothe second LBT. Specifically, the LBT previous to the second LBT refersto previous random backoff CCA-based LBT. Unless otherwise specified,the LBT described in this embodiment of the present invention is randombackoff CCA-based LBT. Details are not described below.

It should be understood that a CWS corresponding to each time of LBTperformed by the terminal device is adjusted based on the CWScorresponding to the previous LBT performed by the terminal device, andthe adjustment includes increasing, keeping unchanged, and reduction.For example, if it is determined that the CWS corresponding to currentLBT is to be increased, the CWS corresponding to the current LBT isincreased to a next higher value in a CWS set compared with the CWScorresponding to the previous LBT. If it is determined that the CWScorresponding to the current LBT remains unchanged, the CWScorresponding to the current LBT remains the same as the CWScorresponding to the previous LBT.

The first CWS and the second CWS correspond to a same access priority.In other words, the first CWS is a CWS of the LBT previous to the secondLBT corresponding to a same access priority as the second CWS.

It should be understood that when accessing a channel, each terminaldevice may perform LBT based on a service type by using one of at leasttwo access priorities (Priority class). Each access priority correspondsto a particular CWS value set. For example, for four access priorities,a CWS set with an access priority 1 is {3, 7}, a CWS set with an accesspriority 2 is {7, 15}, a CWS set with an access priority 3 is {15, 31,63, 127, 255, 511, 1023}, and a CWS set with an access priority 4 is{15, 31, 63, 127, 255, 511, 1023}. Each time the terminal device adjuststhe CWS before performing LBT, an adjustment operation of increasing,decreasing, or keeping the CWS unchanged is performed for each of the atleast two access priorities, and is not limited to an access priorityused for performing the LBT. For example, for the four accesspriorities, before the terminal device performs LBT by using the accesspriority 1, if the CWS needs to be increased, for each of the fouraccess priorities, the CWS is increased to a next higher value in a CWSvalue set corresponding to the access priority, and then a CWS valueadjusted based on the access priority 1 is used to perform LBT.Therefore, a magnitude relationship between any two CWSs described inthis embodiment of the present invention refers to a relationshipbetween two CWSs with a same access priority. For example, that thesecond CWS is greater than the first CWS means that for any accesspriority, the first CWS corresponding to the first LBT is increased tothe second CWS corresponding to the second LBT. For another example,that the second CWS is equal to the first CWS means that for any accesspriority, the second CWS corresponding to the second LBT is kept equalto the first CWS corresponding to the first LBT.

It should be understood that the descriptions of the first CWS and thesecond CWS corresponding to a same access priority are also applicableto another embodiment of the present invention. A magnitude relationshipbetween any two CWSs described in this embodiment of the presentinvention is a relationship between two CWSs with a same accesspriority.

Optionally, that the terminal device does not receive the firstindication information indicating the HARQ status after the first uplinkburst may be that the terminal device does not receive, the firstindication information indicating the HARQ status after the first uplinkburst and before the second uplink burst, or may be that the terminaldevice does not receive the first indication information indicating theHARQ status after the second reference time unit corresponding to thefirst uplink burst and before the first reference time unit, or may bethat the terminal device does not receive the first indicationinformation indicating the HARQ status within a first time thresholdstarting from the second reference time unit corresponding to the firstuplink burst.

Optionally, on condition that the first time length is greater than thefirst time threshold, and the terminal device does not receive firstindication information indicating an HARQ status within a time betweenthe second reference time unit corresponding to the first uplink burstand the first reference time unit, the second CWS is greater than thefirst CWS, where the first CWS is a CWS corresponding to LBT previous tothe second LBT, in other words, the terminal device increases the CWS.As shown in FIG. 3, in a possible case, the terminal device receives, inthe second reference time unit corresponding to the first uplink burst,that is, before the start point of the timer and after the first uplinkburst, the first indication information indicating the HARQ status. Inthis case, for the second uplink burst by which the first reference timeunit exceeds the timer, the terminal device increases the CWS.

Optionally, on condition that the first time length is greater than thefirst time threshold, and the terminal device does not receive firstindication information indicating an HARQ status within the firstreference time threshold starting from the second reference time unitcorresponding to the first uplink burst, the second CWS is greater thanthe first CWS, where the first CWS is a CWS corresponding to LBTprevious to the second LBT, in other words, the terminal deviceincreases the CWS. As shown in FIG. 4, in a possible case, the terminaldevice receives the first indication information indicating the HARQstatus after the timer corresponding to the first uplink burst expiresand before the first reference time unit. In this case, for the seconduplink burst by which the first reference time unit exceeds the timer,the terminal device increases the CWS.

In a second manner, on condition that the first time length is less thanor equal to the first time threshold, and the terminal device does notreceive the first indication information indicating the HARQ statusafter the first uplink burst, the second CWS is equal to the first CWS.

It should be understood that the LBT previous to the second LBT refersto previous random backoff CCA-based LBT.

As shown in FIG. 5, the terminal device does not receive the firstindication information indicating the HARQ status after the first uplinkburst, and the first reference time unit corresponding to the seconduplink burst does not exceed a timer T1 corresponding to the firstuplink burst. It should be understood that, as described above, thefirst indication information indicating the HARQ status includes atleast one of HARQ-ACK feedback information and a UL grant. In this case,the terminal device does not increase the CWS. In other words, thesecond CWS is equal to the first CWS, and the first CWS is a CWScorresponding to the LBT previous to the second LBT.

Optionally, in this possible design, when the second reference time unitcorresponding to the first uplink burst meets the case 3 describedabove, that the terminal device determines the second CWS includes: Whenthe first reference time unit is not later than the second referencetime unit corresponding to the first uplink burst, or when the firsttime length is less than the first time threshold, and the terminaldevice does not receive, between the second reference time unitcorresponding to the first uplink burst and the first reference timeunit, the first indication information including the HARQ status, theterminal device does not increase the CWS. In other words, the secondCWS is equal to the first CWS, and the first CWS is a CWS correspondingto the LBT previous to the second LBT.

Optionally, in a third manner, on condition that the first time lengthis less than or equal to the first time threshold, and the terminaldevice does not receive the first indication information indicating theHARQ status after the first uplink burst, the second CWS is determinedbased on second indication information, where the second indicationinformation is indication information that is received by the terminaldevice before the first uplink burst and that is used to indicate theHARQ status.

As shown in FIG. 6, the terminal device does not receive the firstindication information indicating the HARQ status after the first uplinkburst, and the first reference time unit corresponding to the seconduplink burst does not exceed a timer T1 corresponding to the firstuplink burst. It should be understood that, as described above, thefirst indication information indicating the HARQ status includes atleast one of HARQ-ACK feedback information and a UL grant. In this case,the terminal device determines the second CWS based on the HARQ statusinformation before the first uplink burst. The terminal device mayadjust the CWS based on the HARQ status information by using a method inthe prior art.

It should be noted that the foregoing three manners may be used asindependent solutions, or any two of the foregoing three manners areused as an overall solution, or the three solutions may be used as anoverall solution.

Optionally, in a possible design, on condition that the first timelength is greater than or equal to the first time threshold, and theterminal device does not receive, within a time after the first uplinkburst and before the second uplink burst, the first indicationinformation indicating the HARQ status, and the second uplink burst isan uplink burst immediately after a third reference time unitcorresponding to the first uplink burst, the terminal device increasesthe CWS. In other words, the second CWS is greater than the first CWS,the first CWS is a CWS corresponding to the LBT previous to the secondLBT, and the third reference time unit corresponding to the first uplinkburst is later than the second reference time unit corresponding to thefirst uplink burst, a time interval between the third reference timeunit corresponding to the first uplink burst and the second referencetime unit corresponding to the first uplink burst is the first timethreshold. It should be understood that the third reference time unitcorresponding to the first uplink burst is an end time unit of the timercorresponding to the first uplink burst. In this possible design, theterminal device increases the CWS only for the first uplink burst thatappears after the timer corresponding to the first uplink burst expires.Optionally, the second uplink burst may be the first AUL uplink burstafter the third reference time unit corresponding to the first uplinkburst. Optionally, the second uplink burst may be a 1^(st) uplink burston which random backoff CCA-based LBT is performed, after the thirdreference time unit corresponding to the first uplink burst. Optionally,the second uplink burst may be a Pt AUL uplink burst on which randombackoff CCA-based LBT is performed, after the third reference time unitcorresponding to the first uplink burst.

The terminal device performs the method provided in this embodiment ofthe present invention, and determines the CWS with reference to a timethreshold, for example, a timer. The time threshold, for example, thetimer, is set, so that the CWS is increased if the first reference timeunit exceeds the timer and no HARQ status information is received,thereby avoiding that because there is a delay in feeding back the HARQstatus information, the CWS is increased when HARQ status informationfed back by a network device is not received within a time interval (forexample, a time interval less than the delay) after one uplink burst.Therefore, it is avoided that a success rate of accessing a channel bythe terminal device is reduced due to an excessive increase of the CWS,so that the terminal device can more properly adapt to a channel statuswhen performing AUL uplink transmission.

FIG. 8 is a schematic process diagram of a method for listening on anuplink channel according to an embodiment of the present invention. FIG.9 and FIG. 10 are sequence diagrams of a method according to anembodiment of the present invention. The following describes the methodprovided in the embodiments of the present invention with reference toFIG. 8 to FIG. 10.

Step 810: A terminal device sends a first data packet on a first uplinkburst.

Step 820: The terminal device performs first LBT.

The operation in this step may be implemented by a modem processor 124of a terminal device in FIG. 12.

Step 830: Send a second data packet on a second uplink burst after thefirst LBT succeeds, where the second uplink burst is later than thefirst uplink burst.

The sending action in the foregoing step may be implemented by thetransceiver 121 of the terminal device in FIG. 12. Certainly, the actionmay alternatively be implemented by a modem processor 124 of theterminal device in FIG. 12 by controlling the transceiver 121.

Step 840: The terminal device determines a second contention window sizeCWS.

An interval between a first reference time unit and a second referencetime unit that corresponds to the first uplink burst is a first timelength, and an interval between the first reference time unit and asecond reference time unit that corresponds to the second uplink burstis a second time length.

In a first manner, on condition that the second time length is less thana first time threshold, and the first time length is greater than orequal to the first time threshold, the terminal device does not receivefirst indication information indicating an HARQ status after the firstuplink burst, and a first CWS corresponding to the first LBT is notincreased compared with a third CWS, the second CWS is greater than afourth CWS, where the fourth CWS is a CWS corresponding to LBT previousto second LBT, and the third CWS is a CWS corresponding to LBT previousto the first LBT.

In a second manner, on condition that the second time length is lessthan a first time threshold, and the first time length is greater thanor equal to the first time threshold, the terminal device does notreceive first indication information indicating an HARQ status after thefirst uplink burst, and a first CWS corresponding to the first LBT isincreased compared with a third CWS, the second CWS is equal to a fourthCWS, where the fourth CWS is a CWS corresponding to LBT previous tosecond LBT, and the third CWS is a CWS corresponding to LBT previous tothe first LBT.

Specifically, if a third uplink burst exceeds a timer corresponding tothe first uplink burst, in other words, the first time length is greaterthan or equal to the first time threshold, when there is a second uplinkburst between the first uplink burst and the third uplink burst, where aCWS corresponding to the second uplink burst is an adjusted CWS, and thefirst reference time unit does not exceed a timer corresponding to thesecond uplink burst, in other words, the second time length is less thanthe first time threshold, the terminal device does not increase thesecond CWS. In other words, the terminal device restarts a new timer forthe second uplink burst on which the CWS has been adjusted, anddetermines, based on a receiving status of an HARQ status and a timeinterval between the second uplink burst and the third uplink burst, aCWS corresponding to the third uplink burst.

Further, that the terminal device adjusts the CWS for the second uplinkburst means that the terminal device increases the CWS for the seconduplink burst. In other words, if there is an uplink burst between thefirst uplink burst and the third uplink burst, and a CWS correspondingto the uplink burst remains unchanged compared with a CWS correspondingto previous LBT, or is decreased compared with a CWS corresponding toprevious LBT, the terminal device needs to increase the second CWS. Theterminal device does not increase the second CWS corresponding to thethird uplink burst only when the CWS corresponding to the second uplinkburst is increased, to avoid repeatedly punishing the CWS. If the seconduplink burst keeps the CWS unchanged or decreases the CWS, the terminaldevice increases the CWS, that is, the second CWS is greater than thefourth CWS, where the fourth CWS is a CWS corresponding to the LBTprevious to the second LBT. It should be understood that the LBTprevious to the second LBT refers to previous random backoff CCA-basedLBT.

Optionally, the CWS corresponding to the second uplink burst may beincreased based on indication information including an HARQ status. Asshown in FIG. 7, for example, HARQ status information received by theterminal device before the first uplink burst is a NACK. Therefore, theterminal device increases the CWS corresponding to the second uplinkburst.

Optionally, the CWS corresponding to the second uplink burst may beincreased due to HARQ status reception timeout. As shown in FIG. 8, forexample, the second uplink burst exceeds a timer of a previous burst,and no HARQ status information is received between the two bursts.Therefore, the terminal device increases the CWS corresponding to thesecond uplink burst.

It should be noted that the first manner and the second manner hereinmay be used as an overall solution, or may be used as independentsolutions.

The operation in this step may be implemented by a modem processor 124of a terminal device in FIG. 12.

Step 850: Perform the second LBT based on the second CWS.

The operation in this step may be implemented by the modem processor 124of the terminal device in FIG. 12.

Step 860: Send a third data packet on the third uplink burst oncondition that the second LBT succeeds, where the third uplink burst islater than the second uplink burst.

The sending action in this step may be implemented by a transceiver 121of the terminal device in FIG. 12. Certainly, the action mayalternatively be implemented by the modem processor 124 of the terminaldevice in FIG. 12 by controlling the transceiver 121.

It should be understood that the foregoing descriptions of the CWS andthe LBT are also applicable to this embodiment, and details are notdescribed herein again.

In a possible design, the first reference time unit is a time unit inwhich the terminal device determines the second CWS. For example, if theterminal device determines the second CWS in a TTI, the first referencetime unit is the TTI or a start time unit of the third uplink burst. Forexample, the start time unit may be a start time unit determined by theterminal device based on a time sequence relationship.

Optionally, the second reference time unit corresponding to the firstuplink burst is a time unit in the first uplink burst; or the secondreference time unit corresponding to the first uplink burst is a timeunit that has an interval of a third time length from a start time unitof the first uplink burst, and the second reference time unit is afterthe start time unit of the first uplink burst; and the second referencetime unit corresponding to the second uplink burst is a time unit in thesecond uplink burst; or the second reference time unit corresponding tothe second uplink burst is a time unit that has an interval of a thirdtime length from a start time unit of the second uplink burst, and thesecond reference time unit is after the start time unit of the firstuplink burst.

Further, the second reference time unit corresponding to the firstuplink burst may be different from the second reference time unitcorresponding to the second uplink burst.

Optionally, the second reference time unit corresponding to the firstuplink burst is the start time unit of the first uplink burst; or thesecond reference time unit corresponding to the second uplink burst isthe start time unit of the second uplink burst.

Optionally, the first CWS and the third CWS correspond to a same accesspriority, and the second CWS and the fourth CWS correspond to a sameaccess priority.

It should be understood that a CWS corresponding to each time of LBTperformed by the terminal device is adjusted based on the CWScorresponding to the previous LBT performed by the terminal device, andthe adjustment includes increasing, keeping unchanged, and reduction.For example, if it is determined that the CWS corresponding to currentLBT is to be increased, the CWS corresponding to the current LBT isincreased to a next higher value in a CWS set compared with the CWScorresponding to the previous LBT. If it is determined that the CWScorresponding to the current LBT remains unchanged, the CWScorresponding to the current LBT remains the same as the CWScorresponding to the previous LBT.

It should be understood that when accessing a channel, each terminaldevice may perform LBT based on a service type by using one of at leasttwo access priorities (Priority class). Each access priority correspondsto a particular CWS value set. For example, for four access priorities,a CWS set with an access priority 1 is {3, 7}, a CWS set with an accesspriority 2 is {7, 15}, a CWS set with an access priority 3 is {15, 31,63, 127, 255, 511, 1023}, and a CWS set with an access priority 4 is{15, 31, 63, 127, 255, 511, 1023}. Each time the terminal device adjuststhe CWS before performing LBT, an adjustment operation of increasing,decreasing, or keeping the CWS unchanged is performed for each of the atleast two access priorities, and is not limited to an access priorityused for performing the LBT. For example, for the four accesspriorities, before the terminal device performs LBT by using the accesspriority 1, if the CWS needs to be increased, for each of the fouraccess priorities, the CWS is increased to a next higher value in a CWSvalue set corresponding to the access priority, and then a CWS valueadjusted based on the access priority 1 is used to perform LBT.Therefore, a magnitude relationship between any two CWSs described inthis embodiment of the present invention refers to a relationshipbetween two CWSs with a same access priority. For example, that thesecond CWS is greater than the first CWS means that for any accesspriority, the first CWS corresponding to the first LBT is increased tothe second CWS corresponding to the second LBT. For another example,that the second CWS is equal to the first CWS means that for any accesspriority, the second CWS corresponding to the second LBT is kept equalto the first CWS corresponding to the first LBT.

Optionally, the first reference time unit is a time unit in which theterminal device determines the second CWS.

Optionally, the first reference time unit is a start time unit of thesecond uplink burst.

Optionally, the LBT previous to the second LBT is the same as the firstLBT.

Further, the second time length may be predefined or received from anetwork device.

Optionally, the third time length may relate to the delay indicated bythe network device.

According to the method provided in this embodiment, on condition thatthe HARQ status information is not received after the first uplinkburst, and the terminal device has increased the CWS corresponding tothe second uplink burst between the first uplink burst and the thirduplink burst, and the first reference time unit does not exceed timerduration of the second uplink burst, the terminal device does notincrease, because the third uplink burst exceeds timer durationcorresponding to the first uplink burst, the CWS corresponding to thethird uplink burst, but keeps the CWS corresponding to the third uplinkburst unchanged. Compared with the method in which the terminal deviceincreases the CWS provided that the first reference time exceeds thetimer duration, this method can avoid that the CWS is increased againdue to timer expiration when the CWS has been increased in a short time,thereby avoiding excessive penalty on the CWS, and improving propernessof adjusting the CWS by the terminal device in an AUL scenario.

FIG. 11 is a sequence diagram of still another method for listening onan uplink channel according to an embodiment of the present invention.Still another method provided in the embodiments of the presentinvention is described below with reference FIG. 8 and FIG. 11.

Step 810: A terminal device sends a first data packet on a first uplinkburst.

Step 820: The terminal device performs first LBT.

The operation in this step may be implemented by a modem processor 124of a terminal device in FIG. 12.

Step 830: Send a second data packet on a second uplink burst after thefirst LBT succeeds, where the second uplink burst is later than thefirst uplink burst.

Step 840: The terminal device determines a second contention window sizeCWS.

An interval between a first reference time unit and a second referencetime unit that corresponds to the first uplink burst is a first timelength, and an interval between the first reference time unit and asecond reference time unit that corresponds to the second uplink burstis a second time length. On condition that the second time length isgreater than or equal to a first time threshold, and the first timelength is greater than or equal to the first time threshold, and theterminal device does not receive first indication information indicatingan HARQ status after the first uplink burst, the second CWS is a CWSincreased on a basis of a first CWS, and the first CWS is a CWScorresponding to LBT previous to the first LBT.

It should be understood that the foregoing descriptions of the CWS andthe LBT are also applicable to this embodiment, and details are notdescribed herein again.

Specifically, on condition that a third uplink burst exceeds a timercorresponding to the first uplink burst, that is, the first time lengthis greater than or equal to the first time threshold, and the thirduplink burst exceeds a timer corresponding to the second uplink burst,that is, the second time length is greater than or equal to the firsttime threshold, and the terminal device does not receive, after thefirst uplink burst and before the third uplink burst, the firstindication information indicating the HARQ status, the terminal deviceincreases the CWS only once. To be specific, the first CWS is a CWSobtained by increasing the second CWS once, and the second CWS is a CWScorresponding to LBT previous to the first LBT.

As shown in FIG. 9, the third uplink burst exceeds both a timer T1corresponding to the first uplink burst and a timer T2 corresponding tothe second uplink burst, and the terminal device does not receive,between the first uplink burst and the third uplink burst, the firstindication information indicating the HARQ status. In this case, theterminal device increases the CWS only once. Specifically, a first CWScorresponding to the third uplink burst is greater than the second CWS,where the second CWS is a CWS corresponding to the LBT previous to thefirst LBT, and the first CWS is a smallest CWS in CWSs that are greaterthan the second CWS and that are in a set of CWSs having a same accesspriority. It should be noted that a concept of the access priority isdescribed above, and details are not described herein again.

The operation in this step may be implemented by the modem processor 124of the terminal device in FIG. 12.

Step 850: Perform second LBT based on the second CWS.

The operation in this step may be implemented by the modem processor 124of the terminal device in FIG. 12.

Step 860: Send a third data packet on the third uplink burst oncondition that the second LBT succeeds, where the third uplink burst islater than the second uplink burst.

The sending action in the foregoing step may be implemented by thetransceiver 121 of the terminal device in FIG. 12. Certainly, the actionmay alternatively be implemented by a modem processor 124 of theterminal device in FIG. 12 by controlling the transceiver 121.

In a possible design, the first reference time unit is a time unit inwhich the terminal device determines the second CWS. For example, if theterminal device determines the second CWS in a TTI, the first referencetime unit is the TTI or a start time unit of the third uplink burst. Forexample, the start time unit may be a start time unit determined by theterminal device based on a time sequence relationship.

Optionally, the second reference time unit corresponding to the firstuplink burst is a time unit in the first uplink burst; or the secondreference time unit corresponding to the first uplink burst is a timeunit that has an interval of a third time length from a start time unitof the first uplink burst, and the second reference time unit is afterthe start time unit of the first uplink burst; and

the second reference time unit corresponding to the second uplink burstis a time unit in the second uplink burst; or the second reference timeunit corresponding to the second uplink burst is a time unit that has aninterval of a third time length from a start time unit of the seconduplink burst, and the second reference time unit is after the start timeunit of the first uplink burst.

Further, the second reference time unit corresponding to the firstuplink burst may be different from the second reference time unitcorresponding to the second uplink burst.

Optionally, the second reference time unit corresponding to the firstuplink burst is the start time unit of the first uplink burst; or thesecond reference time unit corresponding to the second uplink burst isthe start time unit of the second uplink burst.

Optionally, the first reference time unit is a time unit in which theterminal device determines the second CWS.

Optionally, the first reference time unit is a start time unit of thesecond uplink burst.

Optionally, the first CWS and the second CWS correspond to a same accesspriority.

Optionally, the LBT previous to the second LBT is the same as the firstLBT.

Further, the second time length may be predefined or received from anetwork device.

Optionally, the third time length may be related to a delay of feedingback an HARQ status by the network device.

In the foregoing embodiments, on condition that the first reference timeunit exceeds the first time threshold corresponding to the first uplinkburst, that is, duration of the timer corresponding to the first uplinkburst, and the first reference time unit also exceeds duration of thetimer corresponding to the second uplink burst, and no HARQ statusinformation is received after the first uplink burst, in other words, oncondition that the terminal device exceeds timers corresponding to aplurality of uplink bursts and does not receive the HARQ statusinformation, the terminal device increases the CWS only once, therebyavoiding excessive penalty on the CWS when there are a plurality oftimes of expiration, and improving properness of adjusting the CWS bythe terminal device in an AUL scenario.

FIG. 12 is a possible schematic structural diagram of a terminal device.The terminal device can perform the method provided in the embodimentsof the present invention. The terminal device may be any one of the twoterminal devices 116 and 122 in FIG. 1. The terminal device includes atransceiver 121, an application processor (application processor) 122, amemory 123, and a modem processor (modem processor) 124.

The transceiver 121 may adjust (for example, perform analog conversion,filtering, amplification, and up-conversion on) output sampling andgenerate an uplink signal. The uplink signal is transmitted to thenetwork device in the foregoing embodiment by using an antenna. Indownlink, the antenna receives a downlink signal transmitted by anetwork device. The transceiver 121 may adjust (for example, performfiltering, amplification, down-conversion, and digitalization on) asignal received from the antenna and provide an input sample. Thetransceiver 121 may implement sending and receiving functions of theterminal device in the foregoing method embodiments, including thefunction of sending a data packet in an uplink burst. Technical featuresin the foregoing method embodiments are also applicable to the apparatusembodiment. Details are not described herein again.

The modem processor 124 is sometimes referred to as a controller orprocessor, and may include a baseband processor (baseband processor,BBP) (not shown). The baseband processor processes a receiveddigitalized signal, to extract information or a data bit transmitted inthe signal. Based on a requirement or an expectation, the BBP is usuallyimplemented in one or more digits in the modem processor 124 orimplemented as a separated integrated circuit (IC).

In a design, a modem processor (modem processor) 124 may include anencoder 1241, a modulator 1242, a decoder 1243, and a demodulator 1244.The encoder 1241 is configured to encode a to-be-sent signal. Forexample, the encoder 1241 may be configured to: receive service dataand/or a signaling message that are/is to be sent in an uplink, andprocess (for example, format, encode, or interleave) the service dataand the signaling message. The modulator 1242 is configured to modulatean output signal of the encoder 1241. For example, the modulator mayperform processing such as symbol mapping and/or modulation on theoutput signal (data and/or signaling) of the encoder, and provide anoutput sample. The demodulator 1244 is configured to demodulate an inputsignal. For example, the demodulator 1244 processes an input sample andprovides symbol estimation. The decoder 1243 is configured to decode ademodulated input signal. For example, the decoder 1243 performsprocessing such as de-interleaving and/or decoding on the demodulatedinput signal, and outputs a decoded signal (data and/or signaling). Theencoder 1241, the modulator 1242, the demodulator 1244, and the decoder1243 may be implemented by a combined modem processor 124. These unitsperform processing based on a radio access technology used in a radioaccess network.

The modem processor 124 receives, from an application processor 122,digitalized data that may represent voice, data, or control information,and processes the digitalized data for transmission. The modem processormay support one or more of a plurality of wireless communicationsprotocols of a plurality of communications systems, for example, LTE,new radio, a universal mobile telecommunications system (UniversalMobile Telecommunications System, UMTS), and high speed packet access(High Speed Packet Access, HSPA). Optionally, the modem processor 124may also include one or more memories.

Optionally, the modem processor 124 and the application processor 122may be integrated in one processor chip.

The modem processor 124 may implement the processing function of theterminal device in the foregoing method embodiments, includingdetermining a CWS and performing LBT, or the modem processor 124 mayimplement functions of sending a data packet and performing LBT togetherwith the transceiver 121. The technical features in the foregoing methodembodiments are also applicable to this apparatus embodiment. Detailsare not described herein again.

The memory 123 is configured to store program code (sometimes alsoreferred to as a program, an instruction, software, or the like) and/ordata that are/is used to support communication of the terminal device.

It should be noted that the memory 123 may include one or more storageunits, for example, may be a storage unit that is inside the modemprocessor 124 or the application processor 122 and that is configured tostore program code, or may be an external storage unit independent ofthe modem processor 124 or the application processor 122, or may be acomponent including a storage unit inside the modem processor 124 or theapplication processor 122 and an external storage unit independent ofthe modem processor 124 or the application processor 122.

The modem processor 124 may be a central processing unit (CentralProcessing Unit, CPU), a general-purpose processor, a digital signalprocessor (Digital Signal Processor, DSP), an application-specificintegrated circuit (Application-Specific Integrated Circuit, ASIC), afield programmable gate array (Field Programmable Gate Array, FPGA) oranother programmable logic device, a transistor logic device, a hardwarecomponent, another integrated circuit, or any combination thereof. Themodem processor 124 may implement or execute various example logicalblocks, modules, and circuits described with reference to contentdisclosed in the embodiments of the present invention. The processor mayalso be a combination that implements a computing function device, forexample, a combination including one or more microprocessors, acombination of a DSP and a microprocessor, or a system-on-a-chip(system-on-a-chip, SOC).

A person skilled in the art can understand that various explanatorylogic blocks, modules, circuits, and algorithms described with referenceto the various aspects disclosed in this application may be implementedas electronic hardware, an instruction that is stored in a memory oranother computer readable medium and that is executed by a processor oranother processing device, or a combination thereof. In an example, thedevice described in this specification may be applied to any circuit,hardware component, IC, or IC chip. The memory disclosed in thisapplication may be any type of memory in any size, and may be configuredto store any type of required information. To clearly explain suchinterchangeability, various explanatory components, blocks, modules,circuits, and steps have been generally described above based onfunctionality. How to implement such functionality depends on a specificapplication, a design selection, and/or a design constraint that isimposed on an entire system. A person skilled in the art may usedifferent manners to implement the described functions for eachparticular application, but it should not be considered that suchimplementation goes beyond the scope of the present invention.

The modem processor 124 controls and manages an action of a terminal,and is configured to perform the action performed by the terminal devicein the foregoing embodiment. The transceiver 121 is connected to themodem processor 124 and sends or receives a radio signal by using anantenna, where there may be a single antenna or a plurality of antennas.The memory 123 is configured to store data generated when the terminaldevice performs the method in the embodiments of the present inventionand program code used to support communication of the terminal device.

An example of the present invention further provides an apparatus (forexample, an integrated circuit, a wireless device, or a circuit module),configured to implement the foregoing method. An apparatus forimplementing the method described in this specification may be aself-supporting device or a part of a larger device. The device may be:(i) an independent IC, (ii) a set of one or more ICs, where the set mayinclude a memory IC configured to store data and/or instructions, (iii)an RFIC, such as an RF receiver or an RF transmitter/receiver, (iv) anASIC, such as a mobile station modem, (v) a module that can be embeddedin another device, (vi) a receiver, a cellular phone, a wireless device,or a mobile unit, or (vii) others.

The method and the apparatus that are provided in the embodiments of thepresent invention may be applied to a terminal device. The terminaldevice may include a hardware layer, an operating system layer runningabove the hardware layer, and an application layer running above theoperating system layer. The hardware layer includes hardware such as acentral processing unit (central processing unit, CPU), a memorymanagement unit (memory management unit, MMU), and memory (also referredto as main memory). The operating system may be any one or more computeroperating systems that implement service processing by using a process(process), for example, a Linux operating system, a Unix operatingsystem, an Android operating system, an iOS operating system, or aWindows operating system. The application layer includes applicationssuch as a browser, an address book, word processing software, andinstant messaging software. In addition, a specific structure of anexecution body of the method is not limited in the embodiments of thepresent invention, provided that a program that records code of themethod in the embodiments of the present invention can be run to performcommunication according to the method in this embodiment of the presentinvention. For example, the method in the embodiments of the presentinvention may be executed by a terminal device, or a functional modulethat can invoke a program and execute the program.

A person of ordinary skill in the art may be aware that, in combinationwith the examples described in the embodiments disclosed in thisspecification, units and algorithm steps may be implemented byelectronic hardware or a combination of computer software and electronichardware. Whether the functions are performed by hardware or softwaredepends on particular applications and design constraint conditions ofthe technical solutions. A person skilled in the art may use differentmethods to implement the described functions for each particularapplication, but it should not be considered that the implementationgoes beyond the scope of the embodiments of the present invention.

In addition, aspects or features in the embodiments of the presentinvention may be implemented as a method, an apparatus or a product thatuses standard programming and/or engineering technologies. The term“product” used in this application covers a computer program that can beaccessed from any computer readable component, carrier or medium. Forexample, the computer-readable medium may include but is not limited to:a magnetic storage component (for example, a hard disk, a floppy disk ora magnetic tape), an optical disc (for example, a compact disc (compactdisc, CD), a digital versatile disc (digital versatile disc, DVD), asmart card and a flash memory component (for example, erasableprogrammable read-only memory (erasable programmable read-only memory,EPROM), a card, a stick, or a key drive). In addition, various storagemedia described in this specification may indicate one or more devicesand/or other machine-readable media that are configured to storeinformation. The term “machine-readable media” may include but is notlimited to a radio channel, and various other media that can store,contain, and/or carry an instruction and/or data.

All or some of the foregoing embodiments may be implemented by usingsoftware, hardware, firmware, or any combination thereof. When softwareis used to implement the embodiments, the embodiments may be implementedcompletely or partially in a form of a computer program product. Thecomputer program product includes one or more computer instructions.When the computer program instructions are loaded and executed on thecomputer, the procedure or functions according to the embodiments of thepresent invention are all or partially generated. The computer may be ageneral-purpose computer, a dedicated computer, a computer network, orother programmable apparatuses. The computer instructions may be storedin a computer-readable storage medium or may be transmitted from acomputer-readable storage medium to another computer-readable storagemedium. For example, the computer instructions may be transmitted from awebsite, computer, server, or data center to another website, computer,server, or data center in a wired (for example, a coaxial cable, anoptical fiber, or a digital subscriber line (DSL)) or wireless (forexample, infrared, radio, or microwave) manner. The computer-readablestorage medium may be any usable medium accessible by a computer, or adata storage device, such as a server or a data center, integrating oneor more usable media. The usable medium may be a magnetic medium (forexample, a floppy disk, a hard disk, or a magnetic tape), an opticalmedium (for example, a DVD), a semiconductor medium (for example, asolid-state drive (Solid State Disk, SSD)), or the like.

It should be understood that the description sequence of the foregoingprocesses does not mean an execution sequence in various embodiments inthe embodiments of the present invention. The execution sequence of theprocesses should be determined based on functions and internal logic ofthe processes, and should not be construed as any limitation on theimplementation processes of the embodiments of the present invention.

A person skilled in the art may clearly understand that, for the purposeof convenient and brief description, for a detailed working process ofthe foregoing system, apparatus, and unit, refer to a correspondingprocess in the foregoing method embodiments, and details are notdescribed herein again.

In the several embodiments provided in this application, it should beunderstood that the disclosed system, apparatus, and method may beimplemented in other manners. For example, the described apparatusembodiment is merely an example. For example, the unit division ismerely logical function division and may be other division in actualimplementation. For example, a plurality of units or components may becombined or integrated into another system, or some features may beignored or not performed. In addition, the displayed or discussed mutualcouplings or direct couplings or communication connections may beimplemented by using some interfaces. The indirect couplings orcommunication connections between the apparatuses or units may beimplemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physicallyseparate, and parts displayed as units may or may not be physical units,may be located in one position, or may be distributed on a plurality ofnetwork units. Some or all of the units may be selected based on actualrequirements to achieve the objectives of the solutions of theembodiments.

When the functions are implemented in the form of a software functionalunit and sold or used as an independent product, the functions may bestored in a computer-readable storage medium. Based on such anunderstanding, the technical solutions of the embodiments of the presentinvention essentially, or the part contributing to the prior art, orsome of the technical solutions may be implemented in a form of asoftware product. The software product is stored in a storage medium,and includes several instructions for instructing a computer device(which may be a personal computer, a server, or a network device) toperform all or some of the steps of the methods described in theembodiments of the present invention. The foregoing storage mediumincludes: any medium that can store program code, such as a USB flashdrive, a removable hard disk, a read-only memory (Read-Only Memory,ROM), a random access memory (Random Access Memory, RAM), a magneticdisk, or an optical disc.

The foregoing descriptions are merely specific implementation manners ofthe present invention, but are not intended to limit the protectionscope of the present invention. Any variation or replacement readilyfigured out by a person skilled in the art within the technical scopedisclosed in the present invention shall fall within the protectionscope of the present invention.

What is claimed is:
 1. A method, comprising: performing first listenbefore talk (LBT); sending a first data packet on a first uplink burstafter the first LBT succeeds; determining a second contention windowsize, wherein determining the second contention window size comprises atleast one of following: in response to a determination that a firstreference time unit is after a first time duration starting from asecond reference time unit corresponding to the first uplink burst andthat first indication information indicating an hybrid automatic repeatrequest (HARQ) status is not received after the first uplink burst,increasing a first contention window size to obtain the secondcontention window size; or in response to a determination that a firstreference time unit is within the first time duration starting from asecond reference time unit corresponding to the first uplink burst andthat the first indication information indicating the HARQ status is notreceived after the first uplink burst, maintaining a first contentionwindow size to obtain the second contention window size; and performingsecond LBT based on the second contention window size, wherein: thefirst contention window size is used for a LBT previous to the secondLBT, and the first reference time unit is later than the secondreference time unit corresponding to the first uplink burst; and thefirst reference time unit is a time unit for determining the secondcontention window size, or the first reference time unit is a startingtime unit of a second uplink burst corresponding to the second LBT; andthe second reference time unit corresponding to the first uplink burstis a time unit in the first uplink burst.
 2. The method according toclaim 1, wherein the first indication information indicating the HARQstatus is not received after the first uplink burst comprises: the firstindication information indicating the HARQ status is not received afterthe second reference time unit corresponding to the first uplink burstand before the first reference time unit.
 3. The method according toclaim 1, wherein: the second reference time unit corresponding to thefirst uplink burst is a starting time unit of the first uplink burst; orthe second reference time unit corresponding to the first uplink burstis a time unit that has an interval of a third time length from thestarting time unit of the first uplink burst, and the second referencetime unit is after the starting time unit of the first uplink burst. 4.The method according to claim 1, further comprising: sending a seconddata packet on the second uplink burst when the second LBT succeeds,wherein the second uplink burst is later than the first uplink burst. 5.The method according to claim 1, wherein: one time unit includes one ormore slots; or one time unit includes one or more symbols.
 6. The methodaccording to claim 1, wherein: the first reference time unit is astarting time unit of the second uplink burst; the first reference timeunit is after the first time duration starting from the second referencetime unit corresponding to the first uplink burst comprises: a startingposition of the second uplink burst is after an ending position of thefirst time duration; the first reference time unit is within the firsttime duration starting from the second reference time unit correspondingto the first uplink burst comprises: a starting position of the seconduplink burst is within the first time duration.
 7. A wireless apparatus,comprising: at least one processor; and one or more memories coupled tothe at least one processor and storing program instructions forexecution by the at least one processor to: perform first listen beforetalk (LBT); send a first data packet on a first uplink burst after thefirst LBT succeeds; determine a second contention window size, whereindetermining the second contention window size comprises at least one offollowing: in response to a determination that a first reference timeunit is after a first time duration starting from a second referencetime unit corresponding to the first uplink burst and that firstindication information indicating an hybrid automatic repeat request(HARQ) status is not received after the first uplink burst, increasing afirst contention window size to obtain the second contention windowsize; or in response to a determination that a first reference time unitis within the first time duration starting from a second reference timeunit corresponding to the first uplink burst and that the firstindication information indicating the HARQ status is not received afterthe first uplink burst, maintaining a first contention window size toobtain the second contention window size; and perform second LBT basedon the second contention window size, wherein: the first contentionwindow size is used for a LBT previous to the second LBT, and the firstreference time unit is later than the second reference time unitcorresponding to the first uplink burst; and the first reference timeunit is a time unit for determining the second contention window size,or the first reference time unit is a starting time unit of a seconduplink burst corresponding to the second LBT; and the second referencetime unit corresponding to the first uplink burst is a time unit in thefirst uplink burst.
 8. The wireless apparatus according to claim 7,wherein the first indication information indicating the HARQ status isnot received after the first uplink burst comprises: the firstindication information indicating the HARQ status is not received afterthe second reference time unit corresponding to the first uplink burstand before the first reference time unit.
 9. The wireless apparatusaccording to claim 7, wherein: the second reference time unitcorresponding to the first uplink burst is the start time unit of thefirst uplink burst; or the second reference time unit corresponding tothe first uplink burst is a time unit that has an interval of a thirdtime length from the starting time unit of the first uplink burst, andthe second reference time unit is after the starting time unit of thefirst uplink burst.
 10. The wireless apparatus according to claim 7,wherein the one or more store the program instructions for execution bythe at least one processor to: send a second data packet on the seconduplink burst when the second LBT succeeds, wherein the second uplinkburst is later than the first uplink burst.
 11. The wireless apparatusaccording to claim 7, wherein the first contention window size and thesecond contention window size correspond to a same access priority. 12.The wireless apparatus according to claim 7, wherein: the firstreference time unit is a starting time unit of the second uplink burst;the first reference time unit is after the first time duration startingfrom the second reference time unit corresponding to the first uplinkburst comprises: a starting position of the second uplink burst is afteran ending position of the first time duration; the first reference timeunit is within the first time duration starting from the secondreference time unit corresponding to the first uplink burst comprises: astarting position of the second uplink burst is within the first timeduration.
 13. The wireless apparatus according to claim 7, wherein: onetime unit includes one or more slots; or one time unit includes one ormore symbols.
 14. A non-transitory computer-readable medium storingcomputer executable instructions for execution by at least one processorto: perform first listen before talk (LBT); send a first data packet ona first uplink burst after the first LBT succeeds; determine a secondcontention window size, wherein determining the second contention windowsize comprises at least one of following: in response to a determinationthat a first reference time unit is after a first time duration startingfrom a second reference time unit corresponding to the first uplinkburst and that first indication information indicating an hybridautomatic repeat request (HARQ) status is not received after the firstuplink burst, increasing a first contention window size to obtain thesecond contention window size; or in response to a determination that afirst reference time unit is within the first time duration startingfrom a second reference time unit corresponding to the first uplinkburst and the first indication information indicating the HARQ status isnot received after the first uplink burst, maintaining a firstcontention window size to obtain the second contention window size; andperform second LBT based on the second contention window size, wherein:the first contention window size is used for a LBT previous to thesecond LBT, and the first reference time unit is later than the secondreference time unit corresponding to the first uplink burst; and thefirst reference time unit is a time unit for determining the secondcontention window size, or the first reference time unit is a startingtime unit of a second uplink burst corresponding to the second LBT; andthe second reference time unit corresponding to the first uplink burstis a time unit in the first uplink burst.
 15. The non-transitorycomputer-readable medium according to claim 14, wherein the firstindication information indicating the HARQ status is not received afterthe first uplink burst comprises: the first indication informationindicating the HARQ status is not received after the second referencetime unit corresponding to the first uplink burst and before the firstreference time unit.
 16. The non-transitory computer-readable mediumaccording to claim 14, wherein: the second reference time unitcorresponding to the first uplink burst is the start time unit of thefirst uplink burst; or the second reference time unit corresponding tothe first uplink burst is a time unit that has an interval of a thirdtime length from the starting time unit of the first uplink burst, andthe second reference time unit is after the starting time unit of thefirst uplink burst.
 17. The non-transitory computer-readable mediumaccording to claim 14, wherein the non-transitory computer-readablemedium stores the computer executable instructions for execution by theat least one processor to: send a second data packet on the seconduplink burst when the second LBT succeeds, wherein the second uplinkburst is later than the first uplink burst.
 18. The non-transitorycomputer-readable medium according to claim 14, wherein the firstcontention window size and the second contention window size correspondto a same access priority.
 19. The non-transitory computer-readablemedium according to claim 14, wherein: the first reference time unit isa starting time unit of the second uplink burst; the first referencetime unit is after the first time duration starting from the secondreference time unit corresponding to the first uplink burst comprises: astarting position of the second uplink burst is after an ending positionof the first time duration; the first reference time unit is within thefirst time duration starting from the second reference time unitcorresponding to the first uplink burst comprises: a starting positionof the second uplink burst is within the first time duration.
 20. Thenon-transitory computer-readable medium according to claim 14, wherein:one time unit includes one or more slots; or one time unit includes oneor more symbols.